Tower distribution in a coal burning power plant

ABSTRACT

A tower distributor receives a stream of working media including pulverized coal and a carrier gas in a coal burning power plant. The tower distributor includes a wall structure and one or more flow directing members including diverters, vane members, and/or protuberances. The wall structure defines a flow passageway for the stream of working media and includes an inlet and an outlet spaced from the inlet in an axial direction. Each flow directing member is provided to alter the flow of the working media through the tower distributor.

CROSS REFERENCE TO RELATED APPLICATION

This application Claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/432,338, filed Jan. 13, 2011, entitled“DISTRIBUTOR OF PULVERIZED COAL AND CARRIER AIR FOR EXHAUSTER MILLS”,the entire disclosure of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to a tower distributor in a coal burningpower plant, and more particularly, to a tower distributor including aplurality of working media flow directing structures for providing agenerally even distribution of pulverized coal and carrier air to one ormore burners of the power plant.

BACKGROUND OF THE INVENTION

In a coal burning power plant, pulverized coal is transported through apipe or duct system that connects an exhauster mill to one or moreburners of a furnace. The pulverized coal is typically transportedwithin the pipe system by a carrier gas, e.g., air, which combines withthe pulverized coal to form a heterogeneous stream of working media. Asthe stream of working media moves through the pipe system, the solidparticles of the pulverized coal in the stream of working media tend toconcentrate together in a pattern generally referred to in the art as arope strand. This phenomenon is commonly referred to in the art as“roping”.

Due to the roping phenomenon, attempts to split the stream into multiplesub-streams for transport to respective burners in the furnace may notyield equal amounts of working media being supplied to each of theburners. Unstable combustion and reduced efficiency result from suchunequal distribution of working media into the respective burners.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a towerdistributor is provided that receives a stream of working mediaincluding pulverized coal and a carrier gas in a coal burning powerplant. The tower distributor comprises a wall structure and at least onediverter. The wall structure defines a flow passageway for the stream ofworking media and includes an inlet and an outlet spaced from the inletin an axial direction. Each diverter is located between the inlet andthe outlet and is affixed to an inner surface of the wall structure.Each diverter extends axially and circumferentially along the wallstructure from a first position located at an area of working mediaconcentration downstream from the inlet to a second position downstreamfrom the first position. Further, each diverter defines a flow channelto effect a diversion of a portion of the stream of working media fromthe first position to the second position.

In accordance with a second aspect of the present invention, a towerdistributor is provided that receives a stream of working mediaincluding pulverized coal and a carrier gas in a coal burning powerplant. The tower distributor comprises a wall structure and a pair ofdiverters. The wall structure defines a flow passageway for the streamof working media and includes an inlet and an outlet spaced from theinlet in an axial direction. The diverters are affixed to an innersurface of the wall structure and are located circumferentially adjacentto one another between the inlet and the outlet of the wall structure.The diverters extend along the wall structure in the axial direction andextend circumferentially in opposite directions. The diverters extendfrom respective first positions located at an area of working mediaconcentration downstream from the inlet to respective second positionsdownstream from the respective first positions. Further, the divertersdefine flow channels to effect a diversion of respective portions of thestream of working media from the respective first positions to thecorresponding second positions. The working media flowing through thetower distributor forms a coal rope, and the area of working mediaconcentration defines an area of the coal rope with a higher allocationof pulverized coal than a remaining portion of the coal rope.

In accordance with a third aspect of the present invention, a towerdistributor is provided that receives a stream of working mediaincluding pulverized coal and a carrier gas in a coal burning powerplant. The tower distributor comprises a wall structure, at least onediverter, and at least one adjustable vane member. The wall structuredefines a flow passageway for the stream of working media and includesan inlet and an outlet spaced from the inlet in an axial direction. Eachdiverter is located between the inlet and the outlet and is affixed toan inner surface of the wall structure. Each diverter extends axiallyand circumferentially along the wall structure from a first positionlocated at an area of working media concentration downstream from theinlet to a second position downstream from the first position. The areaof working media concentration is located on a circumferentially opposedside of the wall structure than an exhauster mill fan that delivers thestream of working media to the tower distributor. Further, each diverterdefines a flow channel to effect a diversion of a portion of the streamof working media from the first position to the second position. Eachvane member is attached to the wall structure and extends radiallyinwardly from the inner surface of the wall structure.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the present invention, it is believed that thepresent invention will be better understood from the followingdescription in conjunction with the accompanying Drawing Figures, inwhich like reference numerals identify like elements, and wherein:

FIG. 1 is a side plan view of a portion of a coal burning power plantincluding a tower distributor according to an embodiment of theinvention;

FIG. 2 is a cross sectional view of the tower distributor in FIG. 1taken along line 2-2 in FIG. 1;

FIG. 3 is a cross sectional view of the tower distributor in FIGS. 1 and2 taken along line 3-3 in FIG. 2; and

FIG. 4 is a perspective view of the tower distributor in FIGS. 1-3 shownwith a wall structure of the tower distributor depicted in phantomlines.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiment,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, and not by way oflimitation, a specific preferred embodiment in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and that changes may be made without departing from the spiritand scope of the present invention.

Referring now to FIG. 1, a portion of a coal burning power plant 10 isshown. The power plant 10 includes a conventional exhauster mill fan 12,also known as a coal mill fan, a tower distributor 14, and a pluralityof conventional burners (not shown) downstream from the towerdistributor 14 with respect to a direction of coal flow through thepower plant 10, as generally represented by the line-arrows 16 in FIG.1.

An exhauster mill (not shown) receives coal and a carrier gas; e.g.,air, pulverizes the coal for distribution via the carrier gas, anddirects the pulverized coal and carrier air toward the tower distributor14 via the exhauster mill fan 12. The combination of pulverized coal andcarrier gas is referred to herein as “working media”. The power plant 10includes one or more feed pipes 18 (one shown in FIG. 1) that is/areprovided to distribute the working media from the exhauster mill fan 12to the tower distributor 14.

Referring to FIGS. 2-4, the tower distributor 14 according to aspects ofthe invention will now be described. The tower distributor 14 comprisesa wall structure 20 defining a flow passageway 22 for the stream ofworking media. The wall structure 20 may comprise one or more conduits,and in the embodiment shown the wall structure 20 comprises first andsecond conduits 20A, 20B bolted together. The wall structure includes aninlet 24 that receives the stream of working media from the exhaustermill fan 12 via the feed pipes 18. The wall structure 20 furtherincludes an outlet 26 spaced from the inlet 24 in an axial direction ofthe tower distributor 14, see FIGS. 2 and 3. As illustrated in FIGS. 2and 3, the outlet 26 may supply the working media from the towerdistributor 14 to a plurality of outlet pipes 28, which each deliver aportion of the working media to a burner.

Referring to FIGS. 2-4, the tower distributor 14 further comprises firstand second circumferentially adjacent diverters 30, 32 located betweenthe inlet 24 and the outlet 26. The diverters 30, 32 are affixed to aninner surface 34 of the wall structure 20 and are generally L-shaped incross-section. The diverters 30, 32 define flow channels within the legsof the L-shape to effect a diversion of respective portions of thestream of working media, as will be discussed herein.

The diverters 30, 32 extend axially downstream and circumferentially inopposite directions from one another along the inner surface 34 of thewall structure 20 from entrance portions 30A, 32A of the diverters 30,32 located at respective first positions to outlet portions 30B, 32B ofthe diverters 30, 32 located at respective second positions downstreamfrom the first positions in an axial direction of the tower distributor14 (see FIG. 4). The diverters 30, 32 preferably extend at angles ofabout 35-55 degrees relative to the axial direction, and each diverter30, 32 preferably spans at least about 90° of an inner circumference ofthe wall structure 20.

The entrance portions 30A, 32A of the diverters 30, 32 areadvantageously arranged near the inlet 24 of the tower distributor 14,i.e., slightly downstream from the inlet 24, at an area of working mediaconcentration 40 (see also FIG. 1). The area of working mediaconcentration 40 comprises an area within the tower distributor 14 thathas been found to comprise a higher allocation of pulverized coal than aremaining portion of tower distributor 14 at the same axial location asthe area of working media concentration 40. That is, as the stream ofworking media flows from the exhauster mill fan 12 toward the burners,the phenomenon of roping occurs, as discussed above. The area of workingmedia concentration 40 defines an area within the tower distributor 14where the coal rope comprises a large amount of pulverized coal. Due tothe placement of the entrance portions 30A, 32A of the diverters 30, 32,the diverters 30, 32 redirect portions of the working media from thearea of working media concentration 40 to the second positions at therespective diverter outlet portions 30B, 32B, as will be discussedherein. As shown in FIG. 1, the area of working media concentration 40is located in close proximity to the inlet 24 of the tower distributor14 on a circumferentially opposed side of the wall structure 20 than theexhauster mill fan 12.

As shown in FIGS. 2 and 4, a gap G having a component in thecircumferential direction is formed between entrance portions 30A, 30Bof the respective diverters 30, 32. Preferably, the circumferentialcomponent of the gap spans about 1-10% of the inner circumference of thewall structure 20.

The tower distributor 14 further comprises first and second adjustablevane members 46, 48 attached to the wall structure 20, see FIGS. 2-4.The vane members 46, 48 extend radially inwardly from the inner surface34 of the wall structure 20 and each are associated with a correspondinghandle 50, 52 located outside of the tower distributor 14, see alsoFIG. 1. The handles 50, 52 can be manipulated from outside of the towerdistributor 14 to adjust the orientation of the corresponding vanemember 46, 48 during operation of the power plant 10 to effect a changein flow direction of a portion of the working media flowing through thewall structure 20 near the corresponding vane member 46, 48, as will bediscussed herein. In a preferred embodiment, the handles 50, 52 eachhave a plurality of preset positions, each preset position correspondingto a particular orientation of the corresponding vane member 46, 48. Thepreset positions may be defined, for example, by a handle tine 50A, 52A(FIGS. 3 and 4) engaged in one of a plurality of holes 55 formed inrespective bars 54A, 56A of the handles 50, 52 supported on the wallstructure 20. The combinations of the first and second vane members 46,48 and their corresponding handles 50, 52 are referred to herein asfirst and second vane assemblies 54, 56, see FIGS. 3 and 4.

As shown most clearly in FIG. 2, the first vane assembly 54 is locatedin the circumferential direction between the respective entranceportions 30A, 32A of the first and second diverters 30, 32, i.e., thefirst vane assembly 54 is generally circumferentially aligned with thegap G formed between the entrance portions 30A, 32A. Further, the firstvane assembly 54 may be generally axially aligned with the outletportions 30B, 32B of the first and second diverters 30, 32. As will bedescribed herein, a portion of the working media that passes through thegap G flows toward the first vane member 46, wherein the first vanemember 46 may alter the direction of the portion of working media.

The second vane assembly 56 is located axially downstream from the firstvane assembly 54 and is located in the circumferential directiongenerally midway between respective outlet portions 30B, 32B of thediverters 30, 32. Further, the second vane assembly 56 may be locatedaxially downstream from the first vane assembly 54 and downstream from aradially outwardly tapered downstream end 21 of the first conduit 20A.As will be described herein, the second vane member 48 may alter thedirection of working media flowing nearby.

The tower distributor 14 further comprises first and secondprotuberances 60, 62, which are generally circumferentially aligned withand are downstream from the respective first and second vane members 46,48 in the embodiment shown. The protuberances 60, 62 extend radiallyinwardly from the wall structure 20 and include angled, lower surfaces60A, 60B and 62A, 62B, see FIG. 4. The angled surfaces 60A, 60B and 62A,62B deflect portions of the working media flowing by the protuberances60, 62, as will be discussed herein.

During operation of the coal burning power plant 10, coal and carrierair are delivered to the exhauster mill. The exhauster mill pulverizesthe coal and the exhauster mill fan 12 distributes the pulverized coaland the carrier air to the tower distributor 14 through the feed tubes18.

The stream of working media forms a coal rope in the tower distributor14, as described above. The formation of the coal rope creates the areaof working media concentration 40 near the inlet 24 of the towerdistributor 14 on the opposite side of the wall structure 20 from theexhauster mill fan 12. Portions of the working media in the area ofworking media concentration 40 enter the flow channels defined by thediverters 30, 32 at the respective diverter entrance portions 30A, 32A.These portions of the working media follow the flow channels defined bythe diverters 30, 32 around the inner circumference of the wallstructure 20 and are released by the diverters 30, 32 at the secondpositions by the diverter outlet portions 30B, 32B, i.e., the respectiveflows of working media are diverted by the diverters 30, 32.

As the working media released by the diverter outlet portions 30B, 32Bflows axially downstream, portions thereof may flow past the second vanemember 48. The orientation of the second vane member 48 can be adjustedby the second handle 52 as needed to modify the flow angle of theworking media. A determination may be made for a desired angle of thesecond vane member 48 using an online monitoring system 70,schematically shown in FIG. 1. The online monitoring system 70 maymonitor conditions within the outlet pipes 28. For example, the onlinemonitoring system 70 may indicate that a higher percentage of theworking media is passing into one or more of the outlet pipes 28 thanone or more other ones of the outlet pipes 28, in which case the secondvane member 48 can be adjusted to modify the flow of the working mediathrough the tower distributor 14, thus effecting a change in the amountof working media passing into each of the respective outlet pipes 28.The online monitoring system 70 may monitor one or more operatingconditions within the tower distributor 14 or within the outlet pipes 28to determine the amount of working media passing into the outlet pipes28, as will be apparent to those skilled in the art.

Once past the second vane member 48, the working media flows into thesecond protuberance 62. The angled surfaces 62A, 62B of the secondprotuberance 62 deflect the working media to further separate the flowof working media into substantially equal portions for delivery into therespective outlet pipes 28.

A portion of the working media in the area of working mediaconcentration 40 that is not diverted by the diverters 30, 32 flowsthrough the gap G between the diverter entrance portions 30A, 32A. Asthis portion of the working media flows axially downstream, it flowspast the first vane member 46. The orientation of the first vane member46 can be adjusted by the first handle 50 as needed to modify the flowangle of this portion of the working media. A determination may be madefor a desired angle of the first vane member 46 using the onlinemonitoring system 70, as described above.

Once past the first vane member 46, the working media flows into thefirst protuberance 60. The angled surfaces 60A, 60B of the firstprotuberance 60 deflect the working media to further separate the flowof working media into substantially equal portions for delivery into therespective outlet pipes 28.

The tower distributor 14 described herein is believed to deliver asubstantially equal amount of working media to each of the outlet pipes28 by changing the configuration of the coal rope, such thatsubstantially equal amounts of working media are delivered to each ofthe respective burners. In an embodiment where the outlet pipes 28 feedmultiple fuel injectors (not shown) in a common burner, a substantiallyequal amount of working media is believed to be supplied to therespective fuel injectors.

By delivering a substantially equal amount of working media to each ofthe outlet pipes 28, emission levels of unwanted products, such as CO,NO_(x), and unburned carbon are believed to be reduced. Also, areas ofhigh heat flux within the burners are believed to be reduced, since noneof the burners have excessive amounts of pulverized coal. Moreover, airimbalance within the burners is believed to be minimized, thussubstantially preventing high airflow velocities at fuel nozzle outletsand subsequent unstable combustion.

Additionally, since the tower distributor 14 of the present inventionmerely diverts portions of the working media flowing therethrough, anddoes not mechanically disrupt the flow of working media, a pressure dropof the working media effected by the tower distributor 14 is believed tobe reduced, thus increasing the efficiency of the power plant 10.Further, since the flow directing components within the towerdistributor 14 do not directly impede the flow of the working media butrather redirect or divert the flow of working media, erosion damage tothe flow directing components is believed to be reduced.

While the tower distributor 14 disclosed herein comprises two diverters30, 32, two vane members 46, 48, and two protuberances 60, 62, it isnoted that additional or fewer ones of these respective components couldbe included in the tower distributor 14.

While a particular embodiment of the present invention has beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A tower distributor that receives a stream of working media includingpulverized coal and a carrier gas in a coal burning power plant, thetower distributor comprising: a wall structure defining a flowpassageway for the stream of working media, the wall structure includingan inlet and an outlet spaced from the inlet in an axial direction; andat least one diverter between the inlet and the outlet and affixed to aninner surface of the wall structure, wherein the at least one diverter:extends axially and circumferentially along the wall structure from afirst position located at an area of working media concentrationdownstream from the inlet to a second position downstream from the firstposition; and defines a flow channel to effect a diversion of a portionof the stream of working media from the first position to the secondposition.
 2. The tower distributor of claim 1, wherein the area ofworking media concentration is located on a circumferentially opposedside of the wall structure from an exhauster mill fan that delivers thestream of working media to the tower distributor.
 3. The towerdistributor of claim 2, wherein the area of working media concentrationis located in close proximity to the inlet of the wall structure.
 4. Thetower distributor of claim 3, wherein the working media flowing throughthe tower distributor forms a coal rope, and wherein the area of workingmedia concentration defines an area of the coal rope with a higherallocation of pulverized coal than a remaining portion of the coal rope.5. The tower distributor of claim 1, wherein the at least one divertercomprises two circumferentially adjacent diverters extending axiallydownstream and extending circumferentially in opposite directions. 6.The tower distributor of claim 5, wherein a gap having a component inthe circumferential direction is formed between entrance portions of therespective diverters, the circumferential component of the gap beingabout 1-10% of an inner circumference of the wall structure.
 7. Thetower distributor of claim 1, wherein the at least one diverter extendsat an angle of about 35-55 degrees relative to the axial direction. 8.The tower distributor of claim 1, wherein the at least one diverterextends along at least about 90° of an inner circumference of the wallstructure.
 9. The tower distributor of claim 1, further comprising atleast one adjustable vane member attached to the wall structure, eachvane member extending radially inwardly from the inner surface of thewall structure.
 10. The tower distributor of claim 9, further comprisinga handle for each vane member, each handle being located outside of thetower distributor for adjusting the orientation of the correspondingvane member during operation of the power plant to effect a change inflow direction of a portion of the working media flowing through thewall structure near the corresponding vane member.
 11. The towerdistributor of claim 10, wherein each handle has a plurality of presetpositions, each preset position corresponding to a particularorientation of the corresponding vane member.
 12. The tower distributorof claim 9, further comprising at least one protuberance generallyaxially aligned with each respective vane member, each protuberanceextending radially inwardly from the wall structure downstream from therespective vane member.
 13. A tower distributor that receives a streamof working media including pulverized coal and a carrier gas in a coalburning power plant, the tower distributor comprising: a wall structuredefining a flow passageway for the stream of working media, the wallstructure including an inlet and an outlet spaced from the inlet in anaxial direction; and a pair of diverters affixed to an inner surface ofthe wall structure and located circumferentially adjacent to one anotherbetween the inlet and the outlet of the wall structure, wherein thediverters: extend along the wall structure in the axial direction andextend circumferentially in opposite directions, the diverters extendingfrom respective first positions located at an area of working mediaconcentration downstream from the inlet to respective second positionsdownstream from the respective first positions; and define flow channelsto effect a diversion of respective portions of the stream of workingmedia from the respective first positions to the corresponding secondpositions; and wherein the working media flowing through the towerdistributor forms a coal rope, and wherein the area of working mediaconcentration defines an area of the coal rope with a higher allocationof pulverized coal than a remaining portion of the coal rope.
 14. Thetower distributor of claim 13, wherein the area of working mediaconcentration is located in close proximity to the inlet of the wallstructure on a circumferentially opposed side of the wall structure froman exhauster mill fan that delivers the stream of working media to thetower distributor.
 15. The tower distributor of claim 13, wherein: a gaphaving a component in the circumferential direction is formed betweenentrance portions of the respective diverters, the circumferentialcomponent of the gap being about 1-10% of an inner circumference of thewall structure; and the diverters extend at angles of about 35-55degrees relative to the axial direction and extend along at least about90° of the inner circumference of the wall structure.
 16. A towerdistributor that receives a stream of working media including pulverizedcoal and a carrier gas in a coal burning power plant, the towerdistributor comprising: a wall structure defining a flow passageway forthe stream of working media, the wall structure including an inlet andan outlet spaced from the inlet in an axial direction; at least onediverter between the inlet and the outlet and affixed to an innersurface of the wall structure, wherein the at least one diverter:extends axially and circumferentially along the wall structure from afirst position located at an area of working media concentrationdownstream from the inlet to a second position downstream from the firstposition, the area of working media concentration being located on acircumferentially opposed side of the wall structure than an exhaustermill fan that delivers the stream of working media to the towerdistributor; and defines a flow channel to effect a diversion of aportion of the stream of working media from the first position to thesecond position; and at least one adjustable vane member attached to thewall structure, each vane member extending radially inwardly from theinner surface of the wall structure.
 17. The tower distributor of claim16, wherein the at least one diverter comprises two circumferentiallyadjacent diverters extending axially downstream and extendingcircumferentially in opposite directions, and wherein a gap having acomponent in the circumferential direction is formed between entranceportions of the respective diverters.
 18. The tower distributor of claim17, wherein the at least one vane member comprises two vane members, thefirst vane member being located in the circumferential direction betweenthe respective entrance portions of the diverters and the second vanemember being located in the circumferential direction generally midwaybetween respective outlet portions of the diverters.
 19. The towerdistributor of claim 16, further comprising a handle for each vanemember, each handle being located outside of the tower distributor foradjusting the orientation of the corresponding vane member duringoperation of the power plant to effect a change in flow direction of aportion of the working media flowing through the wall structure near thecorresponding vane member, wherein each handle has a plurality of presetpositions, each preset position corresponding to a particular angle ofthe corresponding vane member.
 20. The tower distributor of claim 16,further comprising at least one protuberance generally axially alignedwith each respective vane member, each protuberance extending radiallyinwardly from the wall structure downstream from the respective vanemember and deflecting working media passing thereby.